Inorganic-polymer complexes for the controlled release of compounds including medicinals

ABSTRACT

This invention relates generally to the production and use of inorganic-polymer complexes for the controlled release of compounds including medicinals. Advantageously, the inorganic used is calcium sulfate.

This is a continuation-in-part of U.S. application Ser. No. 08/935,300,filed Sep. 22, 1997; now U.S. Pat. No. 6,391,336, the entire content ofwhich is hereby incorporated by reference in this application.

FIELD OF THE INVENTION

This invention relates generally to the production and use ofinorganic-polymer complexes for the controlled release of compoundsincluding medicinals.

BACKGROUND OF THE INVENTION

Systemic antibiotic treatment is often unsatisfactory in cases ofosteomyelitis as well as infections in devitalized tissue, avascularscar tissue, and other areas with insufficient blood supply. Increasingblood levels of antibiotics can result in toxicity. For example,aminoglycosides can produce ototoxicity and nephrotoxicity. Anotherproblem with long-term systemic treatment with antibiotics is theselection of drug-resistant mutants. In poorly vascularized areas, theinfectious organism may encounter concentrations below the minimumlethal concentration which provides the opportunity for selection of aresistant form. Also, in large-animal veterinary practice, the cost ofthe antibiotic for systemic use can be an issue.

Antibiotic formulations of polymethylmethacrylate have been employed asantiseptic bone cement and as beads either free or attached to a wirewhich is used for percutaneous removal [H. W. Bucholz, et al, Chiburg.43. 446 (1970)]. PMMA is not bio-erodible.

An alternative is plaster of Paris (POP) which has been used withoutmatrix biopolymers or medicinal complexing agents as CaSO₄.1/2H₂O [D.Mackey, et al, Clin. Orthop., 167, 263 (1982); and G. W. Bowyer, et al,J. Trauma, 36, 331 (1994)]. Polymethylmethacrylate and POP have beencompared with regard to release profiles. Release rates from POP tend tobe very fast.

Both polymethylmethacrylate and POP can be used to produce dimensionallystable beads and other structures. The acrylate cements or beads areformed by mixing pre-formed polymethylmethacrylate polymer,methylmethacrylate monomer, and a free-radical initiator. An exothermicreaction ensues which results in matrix temperatures as high as 100° C.Many antibiotics such as polymyxin and tetracycline are inactivated bythese conditions [G. J. Popham, et al, Orth. Rev. 20, 331 (1991)]. Asmentioned above, polymethylmethacrylate is biocompatible but notresorbable. Therefore, beads used to treat local infection must beretrieved by surgery which is accompanied by the risk of reinfection.

POP beads or pellets are resorbable but show inferior drug releaseprofiles [G. W. Bowyer, et al, J. Trauma, 36, 331 (1994)].

Compositions containing hyaluronic acid have been used for topicaladministration of pharmacological substances [F. Della Valle, et al,U.S. Pat. Nos. 5,166,331 and 4,736,024].

OBJECTS OF THE INVENTION

It is an object of the invention to provide a safe resorbable deliverysystem which enables controlled release of medicinals.

It is an object of the invention to provide a delivery system withcontrollable setting time.

It is a further object of the invention to provide a delivery systemwhich is an injectable liquid which solidifies in a timely way once inplace.

SUMMARY OF THE INVENTION

The subject invention relates to a delivery system comprising:

a) an inorganic compound capable of undergoing hydration and/orcrystalization, and

b) a matrix polymer, and/or

c) a complexing agent.

In another embodiment, the system comprises a complexing agent and amedicinal. Included within the invention are methods of producingsustained release of a medicinal in a mammal by administering the systemwith a medicinal to a mammal. A still further embodiment of theinvention is a method of diagnosing disease in a mammal by administeringa radiopaque matrix to the mammal.

DETAILED DESCRIPTION OF THE INVENTION

The subject invention relates to a resorbable matrix with favorablerelease kinetics. Inorganic compounds such as CaSO₄.1/2 H₂O can becombined with biopolymer in the presence of a bioactive agent includingmedicinals to produce a matrix.

In addition to the inorganic compound there are:

(i) a matrix polymer, and/or (ii) a complexing agent. As used herein,the term “matrix polymer” refers to a polymer (often a biopolymer) whichserves to control the erosion rate, setting time, and influences therelease profile by raising the viscosity of the medium in the pores andchannels of the delivery system. As used herein, the term “complexingagent,” refers to an agent (often a biopolymer), which is used to form asalt or conjugate with the active agent which in effect raises themolecular weight of the active agent and lowers its rate of efflux. Thecomplexing agent is typically a small molecule capable of aggregationwhich has affinity for the active agent. Pharmacologically acceptablehydrophobic medicinal complexing agents include proteins such asalbumin, lipids or cyclodextrins which can be used to complex neutralmedicinal molecules or charged molecules which contain an a polarmoiety. Liposomes containing a medicinal can be entrapped within thecalcium sulfate matrix.

The reaction scheme for forming a matrix including a medicinal is shownbelow:

The consistency and viscosity of the slurry is dependent on the amountand nature of the matrix biopolymer. The slurry can be injected withsubsequent formation of a solid in vivo.

A medicinal can exist in the inorganic-biopolymer complex either free orcomplexed to the medicinal complexing agent. The free compound isreleased relatively fast. The complexed medicinal is released relativelyslowly often contingent on the bioerosion of the inorganic-biopolymercomplex. Antibiotics and local anesthetics are used to illustrate thisprinciple:

The resorbable inorganic-biopolymer complex can contain free antibiotic(e.g., as the sodium salt) or in the form of a biopolymer complex with apolycation such as a polypeptide such as polymyxin B or anaminoglycoside. Lidocaine is conveniently employed as the hydrochloride,the free base, or complexed as the salt of chondroitin sulfate orpolyglutamate.

I. General Considerations

The delivery system of the subject invention for use with medicinalsmust meet the following requirements:

1. Safety—non-toxic, non-immunogenic, non-pyrogenic, non-allergenic.

2. Resorbability—all components should be either assimilable or readilyexcreted.

3. Stability—the matrix should be sterilizable and precursors shouldhave an acceptable shelf-life. Cast forms should be dimensionallystable.

4. Compatibility—the materials and the preparative conditions should notalter the chemistry or activity of the medicinal.

5. Programmability—the residence time and release profile should beadjustable.

There are typically two or three components in the inorganic-polymercomplex matrix

1. An inorganic compound, for example, CaSO₄.1/2H₂O

2. Matrix polymer, for example, hyaluronic acid or dextran

3. Complexing agent, for example, chondroitin sulfate, cationicpolypeptide, or cyclodextrin.

Inorganic Compounds

Calcium sulfate.1/2H₂O (hemihydrate) is the preferred inorganiccomponent. The hemihydrate takes up water and crystallizes as the higherhydrate. Unadulterated calcium sulfate matrix exhibits poor drug releaseprofiles. With matrix polymers and complexing agent-active agentcomplexes the release profiles are improved. Other inorganics may beemployed such as calcium silicates, aluminates, hydroxides and/orphosphates (see pages 72, 95, 327 in Reference Book of InorganicChemistry (1951) Latimer, W. H., and Hildebrand, J. M., Macmillan, NewYork, hereby incorporated by reference in its entirety).

The inorganic compound goes from slurry to solid in a reasonable timeperiod. i.e., 10 minutes-two hours. The matrix biopolymer influences thesetting time and the release profile. Sodium salts and chloride ion actas inhibitors. Sulfate salts and calcium salts accelerate thesolidification process. Calcium pentosan polysulfate containing slurriessolidify faster than those containing sodium as the counterion.

In an advantageous embodiment, the matrix has a porosity sufficient topermit the influx of cells (e.g., osteocytes). See Example 15.

Polymers

In order to slow the efflux of active agent. e.g., medicinal, from thedosage form, polymers, often biopolymers, are included in the matrix toraise the viscosity. Hyaluronic acid (e.g., 1-5%), proteins, e.g.,collagen (gelatin), fibrinogen, which form viscous solutions (e.g.,1-30%), and dextran (e.g., 1-50%) are examples. Viscosity can be changedas a function of time. Hydrolytic enzymes such as a protease, can beincluded to lower the viscosity as a function of time to speed theefflux and compensate for the decrease in the medicinal gradient. Thisfeature provides for a desirable release profile. For medicinal uses,biopolymers (polymers of biological origin) are advantageously employed.

Complexing Agents

To make biopolymer-medicinal complexes for use in parenteral matrices,polymers which are known to be safe are employed. Polymers useful forthis purpose include, but are not limited to, the following:

glycosaminoglycans such as chondroitin sulfate, hyaluronic acid

polynucleotides

acidic proteins

polyglutamic acid

polyaspartic acid

pentosan polysulfate

dextran sulfate

The polymers should be assimilable for use in veterinary or humanmedicine.

In another embodiment, lower molecular weight compounds can be used asthe complexing agent. For example, carboxylic acids such as caprylicacid, undecnlenic acid, piperacillin, penicillin V, nafcillin orcefazolin.

For the complexation of anionic medicinals such as some β-lactamantibiotics advantageous polymers include polypeptide cations such aspolymyxins and aminoglycoside antibiotics such as amikacin. Formedicinals not carrying a net positive or negative charge or those thatpossess a significant amount of a polar character, neutral complexingagents are employed. Examples include cyclodextrins, Polysorb 80 andproteins which bind the medicinals. Small molecules which aggregate andbind the medicinals are alternatives. A polar molecules which formmulti-molecular aggregates can be employed. This type is exemplified byliposomes. A series of active medicinals which possess varying degreesof a polar character can be advantageously employed with the a polarcomplexing agent. Such a series is exemplified by hydrocortisonehemisuccinate-sodium, hydrocortisone, hydrocortisone acetate, andhydrocortisone octanoate.

The rationale for using complexing agents is based on Stokes law:

 D∝1/Mv

D=the diffusion coefficient

M=the molecular weight of the medicinal

v=the viscosity of the medium

Use of complexation biopolymers in effect, raises the molecular weightof the medicinal. The presence of both the matrix biopolymer andmedicinal complexing agent can increase the viscosity within the matrixwhich lowers the diffusivity. Another view of the retardation of releaseconcerns the maintenance of electrical neutrality. In order for thecharged medicinal to diffuse away from the medicinal complexing agent anexternal counterion must first diffuse into the matrix and exchange forthe medicinal.

The medicinal complexing agent serves to delay the release of themedicinal. The medicinal complexing agents can be in the form of acationic polymer such as polypeptide cations, aminoglycosides, ananionic polymer such as chondroitin sulfate and a neutral compound suchas cyclodextrin or a lipid or mixture of lipids. Also, chondroitinsulfate and other polyanions can be used with a tetramethyl-lysinelinker

which is used in anhydride linkage with β-lactam antibiotics (I) or acarboxylated NSAID (II):

Use of a series of medicinal complexing agents of varying size isillustrated by the example of penicillin G ionically complexed toprogressively larger amines: procaine, benzathine, polymyxin, and otherpolypeptide cations. Cationic medicinals may be analogously bound toprogressively larger carboxylate (sulfate) containing compounds. Anenzymatic direst of chondroitin sulfate constitutes a random series ofsizes and is conveniently prepared.

In one embodiment of the invention, there is a complexing agent and amedicinal only (without an inorganic): see e.g., Table 1 compositions E,H, J, K, L and O. In another embodiment of the invention, there is amatrix polymer and a medicinal only (without an inorganic), for example,hyaluronic acid and a medicinal such as an antibiotic or anesthetic.Complexing agents for non-medicinals are discussed in section V“Non-medical Applications.”

Advantageous delivery systems of the invention are shown in Table 1below:

TABLE 1 Formula- CaSO₄ Complexing tion 1/2H₂O Matrix polymer agentMedicinal A 1 g HA - 0.6 ml (2%) 50 mg NF R/100 mgIa B 1 g Dextran-lecithin- 50 mg NF R/100 0.6 ml (20%) 100 mg mgIa C 1 g HA, 0.6 ml (2%)polyglutamic 100 mg lidocaine acid D 1 g HA, 0.6 ml (2%) chon S 100 mgamikacin E — HA, 0.6 ml (2%) chon S Amikacin 100 mg F 1 g Dextran - 6 mlpolymyxin Cef 100 mg (20%) HA, 0.6 ml (2%) G 1 g HA, 0.6 ml (2%) 500 mgHC (10% a.i.) H — HA, 0.6 ml (2%) 500 mg HC (10% a.i.) I 1 g HA, 0.6 ml(2%) 50 mg cis-platin J — HA, 0.6 ml (2%) chon S Lidocaine 100 mg K —HA, 0.6 ml (2%) chon S Morphine 100 mg L — HA, 0.6 ml (2%) chon SHydromorphone 100 mg M 1 g HA, 0.6 ml (2%) 50 mg Imip N 1 g HA, 0.6 ml(2%) 5 mg BMP-2 O — HA, 0.6 ml (2%) polymyxin 100 mg Imip P 1 g — 0.6 mllidocaine 24 mg chon S Q .5 g HA, 1 ml (2%) HA R* 1 g Dextran 200 mg —Lidocaine 100 mg (solid) (solid) S 1 g Gelatin (10%) — Lidocaine 100 mg0.6 ml (solid) R = radiopaque Cef = cefazolin Ia = iodipamide HC =hydrocortisone in CD HA = hyaluronic acid, sodium salt CD =2-hydroxypropyl-(3-cyclodextrin) NF = norfloxacin Chon S = chondroitinsulfate Imip = imipenem LD = lidocaine * Slurry is made with 0.6 ml ofwater.

II. Production of the Inorganic-Biopolymer Complex-Medicinal Matrix andModes of Administration

The basis for formation of the inorganic-biopolymer complex matrix canbe expressed in the following reaction:

The drug, free and complexed to a medicinal complexing agent, isconveniently mixed with calcium sulfate as a finely ground solid. Thematrix biopolymer is included to influence the setting time and the drugrelease profile.

The setting time can be adjusted so that the user can administer theinorganic-biopolymer complex matrix in the form of a liquid using asyringe with a 23 gauge needle or larger. The matrix will solidify soonthereafter. It is convenient to transfer the slurry to the barrel of asyringe using a spatula or second syringe. The plunger is inserted andthe inorganic-biopolymer complex matrix is injected after expulsion ofair. Salts of fatty acids can be included to facilitate release from themold, e.g., 1-3% calcium stearate. Subcutaneous injections are routinelydone with a syringe fitted with a 25-gauge needle. Dispensing into moldscan be accomplished using a syringe fitted with a blunt needle or insome cases a pipette. The liquid injection can be s.c., i.m., or i.p.Advantageously, the administration is done by parenteral injection.

Administration of the solid matrix can be by surgical implant, oral,i.p., i.a, or p.a. Specific sites can be targeted for administration ofthe medicinal such as an anesthetic or anti-inflammatory.

The drug is conveniently employed as a solid which can be finely groundand mixed with the calcium sulfate. The matrix polymer is routinely usedas a solution. In a representative formulation the following proportionsand ingredients are used:

Ingredient Amount Calcium sulfate 1 g Drug 50 mg matrix biopolymer at 2%0.6 ml

If the calcium sulfate amount is set at 1 g, the amount of drug used isin the range of 1-200 mg and the matrix biopolymer in the range of 0.4-3ml. The concentration of the matrix biopolymer ranges from 0.1-50%.

Cooling, of the ingredients prior to mixing slows the reaction.Increased liquid/solid ratios tend to slow the reaction also. Lowmolecular weight alcohols, such as propanol and butanol, significantlyprolong the setting time. The influence of two matrix biopolymers isshown in Table 2.

Polyethylene glycols (PEGs) can be used to suspend medicinals andcalcium sulfate. The solidification is retarded by PEG. Chloride andsodium salts also inhibit solidification. Availability of water also isused as a means to control the rate of solidification. Silversulfadiazine cream solidifies underwater. The isopropanol diffuses outand water diffuses in where it reacts with calcium sulfate-hemihydratewhich results in hardening. The resultant material then slowly releasesthe medicinal. See Example 11. Topical formulations permit selection ofa complexing agent and/or matrix polymer of non-biological origin.Examples include polyethyleneglycol (PEG) and polyvinylpyrrolidone(PVP).

TABLE 2 Change of setting time by matrix biopolymers A. Hyaluronic acid(HA) Calcium sulfate HA (%) Setting time (min) 1 g 0.6 ml (0) 75 1 g 0.6 ml (.2) 60 1 g 0.6 ml (2) 20 B. Dextran Calcium sulfate Dextran (%)Setting time (min) 1 g 0.6 ml (0)  75 1 g 0.6 ml (10) 15 1 g 0.6 ml (20)25 1 g 0.6 ml (50) 80

Dextran (clinical grade) is a convenient accelerator at lowconcentrations. The solutions are less viscous than HA solutions anddextran is inexpensive.

The inorganic-biopolymer complex can be formed as spheres, granules,cylinders, tablets and beads (including microbeads) for injection or foruse in capsules. The latter can be formed by dispersing the slurry intoa rapidly stirring water-immiscible medium. The size of the beads can bedetermined by the amount and nature of the surfactant and the stirringrate. Milling and sieving to produce beads (30-60μ) is an alternativeapproach. For orthopedic and dental use the inorganic-biopolymer complexmatrix can be molded and or carved into specific shapes to conform tovoids in bone structures. Just prior to formation of the intractablesolid, the material is plastic and can be conveniently shaped to fitopenings of irregular geometry.

III. Release Profile

An idealized release profile has three phases. The burst phase is notnecessary for many drugs but would be advantageous for anesthetics andantimicrobics. The maintenance, or zero-order phase, is a desirableresult of the delayed release of the complexed drug. The drop-off,referred to as the closing phase, occurs as the bioerosion process comesto a conclusion. Sub-batches of beads of varying size, drug load, andrelease profile can be blended to provide the desired release profile.

With regard to control of the release profile, one should consider thatthe rate of diffusion is given by

rate=DA(d[m]/dx)  (1)

D=the diffusion coefficient

A=the surface area

d[m]/dx=the medicinal gradient

Also, according to Stokes Law

D∝1/Mv  (2)

D=diffusion coefficient

M=molecular weight

v=viscosity

The use of the medicinal complexing agent will change the effectivemolecular weight of the medicinal. The matrix density and compositionwill influence the internal viscosity of the delivery system.

Simultaneous use of medicinal complexing agents of varying size is usedadvantageously. For example, penicillin G in the form of salts ofpotassium, procaine, polymyxin, and aminoglycosides such as amikacin canbe used. Polyanions with a range of sizes can be produced byenzymatically digesting glycosaminoglycans.

The shape of the delivery device will dictate the surface area. Forexample the surface area of a sphere is given by

A=4πr ²  (3)

The volume of a sphere is given by

V=4/3πr ³  (4)

Combining (3) and (4) gives

A/V=3/r  (5)

According to equation (5) as beads get smaller, the surface area per agiven volume of inorganic-biopolymer complex increases. One cc ofinorganic-biopolymer complex matrix dispersed as small beads deliversdrug faster than one cc dispersed as large beads. The desired zero-orderrelease profile can be approached by using the proper blend of beads ofvarying size.

Residence time in vivo and bio-compatability have been assessed usinghamsters. Inorganic-biopolymer complex matrices were injected (0.3 ml)subcutaneously. At timed intervals the animals were sacrificed todetermine the residence time and the condition of the injection site asjudged by histo/path analysis. All formulations were very welltolerated. The proportion of calcium sulfate or density was an importantfactor in residence time. Denser formulations lasted longer. Calciumsulfate/HA (3/2) show a residence time of 35 days. Calcium sulfate/HA(1/2) showed a residence time of 20 days. Spherical beads (3.2 mm indiameter) made of calcium sulfate/HA (1/1) lasted ten days. Beadscontaining silver benzoate lasted two weeks and were well tolerated withno toxicity to local tissues.

Another means to control the release profile involves drug precursors.As the precursor is converted to the native compound, its avidity(affinity) for the medicinal complexing agent decreases which in turnraises its diffusivity, thus creating a biphasic release profile. Asopposed to release of a molecule that is covalently linked to a polymer,this embodiment is dependent on a change in polarity. Consider thefollowing:

Compound I is positively charged at physiological pH. It is stronglybound to chondroitin sulfate. As it hydrolyzes to form Compound II, thenet charge becomes zero and as a consequence the release is accelerated.A biphasic release profile is the result when free II is included in thedosage form. The release profile can be controlled by the nature of thehydrolyzable group attached to the carboxyl group. The hydrolyzablegroup can be an ester, an anhydride or other labile functionalities.

IV. Medicinals

A. Non-protein Drugs

The delivery systems described herein are well suited for sustainedrelease of: an analgesic, an anesthetic, an anti-addictive preparation(e.g., naltrexone), an anti-microbic, an antiseptic (e.gs, silver ion,and silver sulfadiazine, calcium peroxide, calcium hypochlorite), ananticoagulant, an antineodplastic, an antidepressant, an anti-diabeticagent, an antihyuderdtensive drug, an anti-inflammatory agent, anantinauseant, an anorexic, an antiulcer drug, a cardiovascular drug, achondroprotective agent, a contraceptive, an antihistamine, a diuretic,a hormone/antihormone, an immunosuppressive, a narcotic detoxificationagent, a uricosuric agent, and a wound healing promoter.

A logical alternative to systemic treatment is to employ deliverysystems for local release of antibiotics. In this case, levels muchgreater than the minimum lethal concentration can be achieved in thetherapeutic compartment while blood levels remain low. Inorganicbiopolymer complexes can be implanted as beads after surgicaldebridement or the matrix can be injected as a liquid with subsequentsolidification.

The inorganic-biopolymer complexes containing antibiotics are especiallyuseful in filling cavities in bone produced by osteomyelitis. Placementof antibiotic-inorganic-biopolymer complexes in the vicinity of infectedbone or other tissue results in eradication of the micro-organism andpermits aseptic healing accompanied by resorption of theinorganic-biopolymer complex. When treating bone lesions, bonemorphogenic proteins can also be included to promote growth of new bone.

Inorganic biopolymer complexes are effective for treatment of otherlocal infections, such as joint sepsis, surgical infections, woundinfections, uterine infections, oral-dental-periodontal infections,vainitis, and localized abscesses. Likely infectious agents includeAeromonas, Capnocytophaga. Citrobacter, Clostridium, Edwardsiella,Eiclhenellca, Enterobacter, Enteroccus, E. Coli, Fusobacterium, Hafnia,Kingella, Klebsiella, Moraxella, Morganella, Mycobacterium, Pasturella,Peptostreprococcus, Plesimonas, Proteus, Pseudomonas, Staphylococus,Streptococcus, and Vibrio.

An advantageous antimicrobic for treatment of localized infections hasthe following characteristics:

1. Cidal

2. Broad spectrum

3. Non-toxic to local tissues

4. Soluble and mobile, that is, readily crosses inflamed membranes.

Antiinfectives of special interest include gentamicin, clarithromycin,minocycline and lincomycin, amikacin, penicillin, cefazolin,ciprofloxacin, enrofloxacin, norfloxacin, silver sulfadiazine, imipenem,piperacillin, nafcillin, cephalexin, vancomycin, nystatin, andamphotericin B or salts thereof. Salts of amikacin-piperacillin andamikacin-caprylic acid are useful in that they provide slower release.Further, amikacin acts synergistically with piperacillin and otherβ-lactams.

In high risk surgical procedures, the antibiotic inorganic-biopolymercomplexes can be used prophylactically. In abdominal surgery antibioticbeads can be distributed to provide antibiotic coverage at criticalpoints. Placing antibiotic beads under the incision is oftenadvantageous.

Chondroprotective agents such as chondroitin sulfate, hyaluronic acid,pentosan polysulfate and dextran sulfate can also be used, optionallywith an antiinfective.

Inorganic biopolymer complexes for local delivery of anti-inflammatorydrugs hold great promise for treatment of osteoarthritis, degenerativejoint disease, and other such afflictions. Neutral and charged forms areadvantageously employed together. For example, free hydrocortisone andhydrocortisone succinate complexed to polymyxin is a useful combination;The anti-inflammatory inorganic-biopolymer complexes are placed adjacentto diseased joints, tendon sheaths, etc. Use can accompany arthroscopicprocedures both as an injectable and as pre-formed implants. NSAIDs arealso of interest including naproxen, and disalicylate. NSAIDS, e.g.,analgesics such as aspirin, and other medicinals can be formulated intablet or capsule form for oral administration.

Inorganic-biopolymer complexes for pain control are primarily based onfree and complexed cationic anesthetics such as lidocaine, buvicaine,bupivacaine, chloroprocaine, procaine, etidocaine, prilocaine, dezocine,hydromorphone, etc. An advantageous medicinal complexing agent ischondroitin sulfate. Tablets or beads are especially useful followingarthroscopic procedures. Implants are placed next to the joint capsulelaterally and medially. Pain relief is provided for 3-5 days whichobviates or greatly reduces systemic use of narcotics.

In conjunction with surgical and diagnostic procedures, analgesia andtranquilization can be provided by the use of a complex of chondroitinsulfate and two bio-active compounds—fentanyl and droperidol. Thesimultaneous use of free and bound forms of the active agents providesrapid onset of the desired effects followed by sustained release fromthe polymeric salt.

Antineoplastics such as ifosfamide, cytoxan, carboplatin, cis-platin,leuprolide, doxorubicin, carmustine, bleomycin, and fluorouracil can beformulated in inorganic-biopolymer complexes for regional chemotherapy.In situations in which locally disseminated tumor is discovered andsurgical removal is deemed inadvisable, administration ofinorganic-biopolymer complex via injection is advantageous, Chargedagents can be employed as salts with medicinal complexing agents as wellas free. Neutral molecules can be formulated with cyclodextrins andemulsifiers. Also, following resection, antineoplasticinorganic-biopolymer complexes can placed in the void left by the tumoras a preventative of recurrence.

Radiopaque inorganic-biopolymer complexes can be produced by inclusionof BaSO₄, iodipamide, or other imaging agents in the complex. Theseformulations can be readily visualized radiographically during and aftersurgical procedures.

Pre-formed beads and tablets can be used as prophylactic anti-infectivesand as pain control agents. These inorganic-biopolymer complexes areespecially useful at the conclusion of orthopedic procedures such asjoint arthroscopy and arthroplasty.

B. Medicinal Proteins

As used herein, the term “medicinal” includes proteins as well as smallmolecules. The term “protein” includes naturally occurring proteins,recombinant proteins, protein derivatives, chemically synthesizedproteins, and synthetic peptides. Medicinal proteins useful in thesubject invention include colony stimulating factors (CSF) includingG-CSF, GM-CSF, and M-CSF; ervthropoietin: interleukins, IL-2, IL-4,IL-6, etc; interferons; growth factors (GF) including epidermal-GF,nerve-GF; tumor necrosis factor (TNF); hormones/bioactive peptides;ACTH; angiotensin, atrial natriuretic peptides, bradykynin,dynorphins/endorphins/β-lipotropin fragments, enkephalin;gastrointestinal peptides including gastrin and glucacon; growth hormoneand growth hormone releasing factors; luteinizing hormone and releasinghormone; melanocyte stimulating hormone; neurotensin; opiode peptides;oxytocin, vasopressin and vasotocin; somatostatin; substance P; clottingfactors such as Factor VIII; thrombolytic factors such as TPA andstreptokinase; enzymes used for “replacement therapy,” e.g.,glucocerebrosidase, hexoseaminidase A; and antigens used in preventativeand therapeutic vaccines such as tetanus toxoid and diptheria toxoid.Medicinal proteins of special interest appear below:

Medicinal Clinical Indication G-CSF Adjunct to myelosuppressivechemotherapy Erythropoietin Anemia kidney disease “Replacement” enzymesHeritabie genetic deficiencies of enzymes Hormones endocrine glandfailure, treatment of hormone sensitive cancers, contraception. growthpromotion Cytokines such as colony Immunoadjuvants stimulating factors.e.g., GM-CSF. interferons. e.gs., IFN-alpha. IFN-beta, interleukins.e.gs.. IL-1. IL-2 and IL-6 and TNF Vaccine antigensImmunization-preventative and therapeutic BMP-2 Bone replacement Woundhealing promoters burns. trauma rh-Lysozyme antimicrobic Growth Factorsgrowth promotion Inhibitors/antagonists of the above

V. Non-medical Applications

There are agricultural and industrial applications of the matrices ofthe invention. The polymers are not necessarily of biological origin.For example, the matrix polymer can be selected from the following:polyethyleneglycol, polyvinylpyrrolidone, polyvinylalcohol, starch,xanthan, cellulose and cellulose derivatives (e.g.,carboxymethylcellulose). Examples of non-ionic complexing agents includepolyoxyethylene esters and ethers, and surfactants of either biologicalor non-biological origin. Examples of ionic complexing agents includepolyacrylic acid, alginic acid, dextran sulfate, polyvinylpyridine,polyvinylamine, polyethyleneimine as well as synthetic lipid compounds.

Examples of bioactive compounds which can be used with the matrix of theinvention include sterilants, pheromones, herbicides, pesticides,insecticides, fungicides, algicides, growth regulators, nematicides,repellents, and nutrients.

The following Examples are illustrative, but not limiting of thecompositions and methods of the present invention. Other suitablemodifications and adaptations of a variety of conditions and parametersnormally encountered which are obvious to those skilled in the art arewithin the spirit and scope of this invention.

EXAMPLES Example 1

Preparation of a Radiopague Norfloxacin-inorganic-biopolymer Complex

CaSO₄.1/2H₂O is sterilized by heating at 120° C. for 4 hours and thendivided into 1 g aliquots which are stored in individual plasticcontainers in a desiccator. Calcium sulfate(1 g), 50 mg norfloxacin, and110 mg iodipamide, all finely ground, are mixed thoroughly. To thismixture is added 0.6 ml of cold hyaluronic acid solution (2%). Theslurry is mixed to an even consistency and is loaded into the barrel ofa 3 ml syringe with a spatula. The plunger is replaced and the airexpelled. The needle is attached to the syringe and theinorganic-biopolymer complex is ready for administration or casting in amold.

Example 2

Preparation of Lidocaine Matrix

Calcium sulfate-hemihydrate (1 g) was mixed with finely ground dextran(clinical grade, 0.2 g) and lidocaine (0.1 g). The solid mixture wasthen stirred with 0.6 ml of water or alternatively 0.6 ml of HA (2%).The slurry was apportioned into screw-cap vials, 0.2 ml each. After 24hr. at room temperature, the samples were refrigerated. The releaseexperiments were done at 37° C. using 1 ml of buffer per vial withchanges at 24 hr. intervals. The release buffer was PBS containing 0.1%sodium azide. The concentration of lidocaine was determinedspectrophotometrically (260 nm). See Table 3 below

TABLE 3 Release of Lidocaine for Matrices with (B) and without (A) theMatrix Biopolymer. Matrix A Matrix B (11% Dextran) Day % Release Day %Release 1 85 1 24 2 10 2 26 3 1 3 22 4 1 4 15 5 1 5 6

Example 3

Preparation of an Inorganic-biopolymer Complex Containing Bound and FreeAmikacin

Chondroitin sulfate solution (sodium salt, 5%) is converted to the acidform by passage over a column of Dowex-50. Assuming a residue molecularweight of 500, a stoichiometric amount of amikacin free base is added at0-4° C. The pH is adjusted to 7 and the product is frozen.Alternatively, the product is freeze-dried and stored in a desiccator.Using chondroitin sulfate as the medicinal complexing agent, othercomplexes can be made by this procedure. Lidocaine, morphine,gentamicin, clindamycin, and doxorubicin are examples.

Calcium sulfate (1 g) is thoroughly mixed with 50 mg of chondroitinsulfate-amikacin (above) and 25 mz amikacin sulfate(1:2). Hyaluronicacid solution (0.6 ml, 2%) is added and the mixture handled as describedin Example 1.

Example 4

Preparation of Cis-platin Beads

Calcium sulfate (1 g) is mixed with 50 mg of finely ground cis-platin(cis-diaminedichloroplatinum). To this mixture 0.6 ml of hyaluronic acidsolution (2%) is added and the slurry is transferred to a 3 ml syringeas described in Example 1. Using a 20-gauge blunt end needle, theinorganic-biopolymer complex is injected into a teflon mold withspherical holes which are 3.2 mm in diameter. After 48 hours at roomtemperature, the mold is split and the beads are removed with a dentalexplorer under sterile conditions. Beads are placed in slits madesurgically around a tumor or around the site of tumor removal in aneffort to prevent recurrence.

Example 5

Preparation of Cefazolin-inorganic-biopolymer Complex

Polymyxin sulfate solution (10%) is cooled to 0-4° C. A stoichiometricamount of barium hydroxide solution is added to produce the free base ofpolymyxin and insoluble barium sulfate. Four equivalents of cefazolin,dissolved in 50% THF, are added. After trituration, the suspension isfiltered to remove the barium sulfate. The residue is washed to recoverall of the conjugate. The solvent of the combined filtrate and washingis evaporated and the polymyxin-cefazolin salt is used as the solid.Calcium sulfate (1 g) is mixed with 100 mg of polymyxin-cefazolin saltand 50 mg of cefazolin-sodium. To this solid mixture is added 0.6 ml ofhyaluronic acid (2%). The slurry is administered directly or placed in abead or tablet mold. Other basic polypeptides, or aminoglycosides may beused in place of polymyxin.

Example 6

Penicillin G-inorganic-biopolymer Complex

Penicillin G is employed simultaneously as the salt of potassium,procaine, benzathine, and polymyxin. To 2 g of calcium sulfate is added100 mg of penicillin G-potassium plus 100 mg procaine-penicillin and 50mg each of polymyxin-penicillin and amikacin-penicillin. After thoroughmixing, 1.2 ml of 20% dextran is added and the slurry handled asdescribed above.

Example 7

An anti-inflammatory Inorganic-biopolymer Complex

An a polar medicinal complexing agent such as Polysorb 80 is employedwith the following forms of hydrocortisone:

A=hydrocortisone hemisuccinate-sodium

B=hydrocortisone

C=hydrocortisone acetate

D=hydrocortisone octanoate

To 1 g of calcium sulfate is added 25 mg each of A, B, C, and D above.To this mixture is added 0.6 ml of 20% dextran plus 100 ul of Polysorb80. The slurry is handled as described above.

Example 8

Herbicide (Dinoseb) Inorganic-polymer Composite

Dinoseb is conjugated with polyethyleneimine (PEI) using water as asolvent. To 1 ml of a PEI solution (10%) is added 200 mg of dinoseb andthe pH is adjusted to near neutrality. This mixture (600 mg) is combinedwith 1 g of calcium sulfate and the slurry used to produce beads with awater-immiscible medium such as sesame oil. Naphthalene acetic acid canbe used in place of dinoseb to produce a long-lasting root growthstimulator.

Example 9

Treatment of a Bone Infection

A colt, aged three months, sustained a fracture which was successfullytreated surgically to the point at which an infection (Enterobacter)occurred. A matrix including norfloxacin (formulation A of Table 1) wasused to treat the infection. After thorough debridement of the cavity,the void was filled with freshly prepared matrix. No surgicalintervention was necessary after the treatment. The infection waseradicated and no sign of lameness appeared after 1 month.

Example 10

Preparation of the Salt, Amikacin-chondroitin Sulfate

Chondroitin sulfate (1 g) is dissolved in 4 ml distilled water at 0-4°C. TCA (1 ml ml, 32%) at 0° C. is added with stirring. The solution ispoured into 20 ml of cold ethanol; the precipitate is collected on afilter, washed and dried. One equivalent of solid amikacin (free base)is added. The solution is adjusted to pH 7.4. It can be used as is orsupplemented with amikacin sulfate.

Example 11

Preparation of Silver Sulfadiazine Cream—a Topical Anti-infective

Component A—520 g of PEG 400 plus 200 g PEG 3350 warmed to form a singlephase (40-500°).

Component B—60 g of PVP K-30 dissolved in 170 ml of anhydrousisopropanol

Component C—20 g of silver sulfadiazine (micronized) suspended in 30 mlof anhydrous isopropanol

Preparation: Components A, B, and C are mixed with stirring at 45-55°.To this suspension 1 kg of calcium sulfate hemihydrate is araduallyadded with stirring. After mixing is complete, the product istransferred to a polypropylene vessel and stored at room temperature orbelow. The product is protected from light. Viscosity can be reduced byincreasing the relative amount of PEG 400 with regard to PEG 3350. Theconverse is also true. The weight of calcium sulfate can be reduced by50% with the other component weights held constant. The product is thenpackaged into 32 ml syringes with nozzle end caps and polyethyleneseals.

Use: Silyer sulfadiazine cream is indicated for treatment of equinethrush and white line disease. After removal of foreign matter andnecrotic tissue, silver sulfadiazine cream is applied to the hoof withconcentration on the cleft of the frog. For best results the syringe isused at 70-90°. The product is particularly advantageous forprophylactic use under shoes or pads at each shoeing.

Example 12

Silver Sulfadiazine Paste—a Topical Anti-infective for Equine HoofRebuilding

Component A—Silver sulfadiazine cream (above)

Component B—2% Hydroxypropyl methylcellulose in 50% alcohol (e.g.,methanol, ethanol, propanol, isopropanol)

Preparation: At 30-40° two parts of Component A are mixed with one partComponent B to form a thick paste. This product is stored in closedpolypropylene tubs and protected from light.

Use: Following hoof resection silver sulfadiazine paste is applied witha spatula to fill voids and reshape the hoof. It can be used underunmedicated plastic hoof rebuilders.

Example 13

Silver Sulfadiazine Beads—a Topical Anti-infective

Preparation: 1 g of calcium sulfate-hemihydrate and 75 mg of silversulfadiazine (USP, micronized) are thoroughly mixed. A slurry is madewith 0.5 ml of Solution D. The solid which forms is ground to a powder;Particle size of <50 microns works well. Solution D is 10% dextransulfate (sodium form, USP, MW=8,000) which is sterile filtered.

Use: These beads can be used directly on open wounds. Incorporation in anon-aqueous organic ointment base is useful; white petrolatum is a goodchoice as is polyethylene glycol based preparations. Suspension of thesebeads in propylene glycol or other liquid vehicle is valuable fortreatment of Otitis Externa.

Example 14

Silver Sulphadiazine Film—a Topical Anti-infective

The films are cast using 2% HPMC in 50% alcohol. The silver sulfadiazinebeads (1-5% by wt.) described above are dispersed into the HPMC solutionand the dispersion is poured onto a glass or plastic surface. Solventevaporation results in a very strong film. Other film formingtechnologies are also applicable. These films can be incorporated intowound dressings and bandages. The film is stable in air but dissolveswhen in contact with water or moist tissue. Once in contact withmoisture the microbeads begin releasing silver sulfadiazine, which isactive against a broad spectrum of bacteria, yeast, and fungi.

Example 15

Porous Orthopedic Filler

This preparation can be used to fill extraction sockets, periodontaldefects, orthopedic defects, root canals, and screw channels followingfracture repair, etc. Porosity allows the penetration of cells such asosteocytes. Bioactive agents such as anti-infectives and osteogeniccompounds can be included to promote bone resorption in a sterileenvironment as the matrix is resorbed.

Component A=Ca(H₂PO₄)₂/NaHCO₃ (1/1)

Component B=Calcium sulfate-hemihydrate

Component C=Biopolymer solution, e.g., Solution D from Example 13

Component A (0.1-0.3 g) and Component B (0.7-0.9) are thoroughly mixed(total=1 g). This solid mixture is then blended with 0.6 ml ofbiopolymer solution. The slurry is immediately injected and allowed tosolidify in situ. Amikacin sulfate (50-100 mg) can be included as theantibiotic.

Example 16

Preparation of Sterile Amikacin Matrix

Calcium sulfate-hemihydrate is sterilized by dry heat—120° for 4 hrs.Solution A is prepared as follows. Dextran sulfate (1 g/CAS9011-18-1) isdissolved in 10 ml of water along with 3 g of amikacin sulfate (CAS39831-55-5). The solution is filtered (0.2 micron filter) into sterileserum cap vials. To 1 g of calcium sulfate-hemihydrate is added 0.5-0.7ml of Solution A. The components are mixed thoroughly to produce auniform slurry. The slurry can be injected directly into the patient,injected into a mold, or used to produce microbeads. Operationsincluding mixing and beyond are conducted is a sterile space. Molds for3-mm beads are sterilized by ethylene oxide treatment. Milling equipmentis sterilized by autoclaving or by treatment with ethylene oxide.

Example 17

Treatment of Equine Joint Sepsis

Infection of the equine joint is characterized by heat, swelling, painon palpation/flexion, and lameness. The use of amikacin beads ispreceded by through-and-through lavage or other joint drainage/flushingtechnique. Amikacin beads are suspended in lactated Ringer's solutionand injected, i.a., with an 18 ga needle. Dosages range from 100-500 mg.Systemic antibiotics may be used as an adjunct. Culture to showsusceptibility is obviously desirable. If amikacin beads are notindicated, cefazolin matrix beads may be employed. Larger beads, 3 mm,can be placed within the joint capsule using the arthroscope or acannula.

Represenative results with amikacin beads (100 mg) are as follows:

Case 1. Luxated LR fetlock with exposure of distal M3. Prior treatmentconsisting of extensive joint flushing, and systemic antibiotictreatment was unsuccessful—persistent positive cultures for Staph, andStrep. Injection of 100 mg of amikacin beads resulted in resolution ofthe infected condition—no more flaring, heat, or positive cultures.Horse returned to sound condition.

Case 2. Puncture wound of the RR fetlock resulted in sepsis of thetendon sheath. Surgery including annular resection systemic antibiotictherapy did not result in correcting the condition. Amikacin beads wereinjected and infection (Staph.) was eradicated as judged by culture andsymptoms. Horse returned to sound condition.

Case 3. Puncture wound of left hock joint resulting in an infection.Horse was treated immediately with amikacin microbeads and the treatmentrepeated after one week. Infection was resolved; horse returned totraining.

It will be readily apparent to those skilled in the art that numerousmodifications and additions may be made to both the present invention,the disclosed device, and the related system without departing from theinvention disclosed.

What is claimed is:
 1. A method of producing sustained release of anactive agent in a mammal comprising administering to said mammal a solidcomposition comprising an active agent which is dispersed throughout asolid matrix reaction product of an aqueous mixture comprised of: a)active agent, b) calcium sulfate hemihydrate c) a matrix polymer, and/ord) a complexing agent, and wherein said composition is in the form of abead, wafer, tablet, sphere, granule or cylinder.
 2. A method as inclaim 1, wherein said solid composition is a reaction product of anaqueous mixture comprised of: a) active agent, b) calcium sulfatehemihydrate and c) a matrix polymer.
 3. A method as in claim 2, whereinsaid matrix polymer is a biopolymer selected from the group consistingof hyaluronic acid, chondroitin sulfate, dextran, and protein.
 4. Amethod as in claim 3, wherein said solid composition comprises an activeagent, calcium sulfate and hyaluronic acid.
 5. A method as in claim 2,wherein said solid composition comprises an active agent, calciumsulfate and a glycosaminoglycan.
 6. A method as in claim 5, wherein saidglycosaminoglycan is hyaluronic acid or chondroitin sulfate.
 7. A methodas in claim 1, wherein there is no matrix polymer and said complexingagent is selected from the group consisting of chondroitin sulfate,polyglutamic acid, polyaspartic acid, polynucleotides, a cationicpolypeptide, cyclodextrin, polyoxyethylene alcohol, ester or ether, anddefatted albumin.
 8. A method as in claim 7, wherein saidpolyoxyethylene alcohol, ester or ether is a surfactant.
 9. A method asin claim 7, wherein said complexing agent is a lipid or a liposome. 10.A method as in claim 9, wherein said lipid is a lipid of biologicalorigin selected from the group consisting of cholesterol and lecithin.11. A method as in claim 7, wherein said complexing agent is a polar.12. A method as in claim 7, wherein said complexing agent is two or morecomplexing agents of more than one size.
 13. A method as in claim 12,wherein said two or more completing agents are selected from the groupconsisting of procaine, benzathin, polymyxin, and a polymer of cationicamino acids.
 14. A method as in claim 12, wherein said two or morecomplexing agents are condroitin sulfate fragments of more than onesize.
 15. A method as in claim 7, wherein said complexing agent is acomplexing agent selected from the group consisting of a polyoxyethyleneester or ether, and a surfactant of either biological or non-biologicalorigin.
 16. A method as in claim 7, wherein said complexing agent isselected from the group consisting of polyacrylic acid, alginic acid,dextran sulfate, polyvinylpyridine, polyvinylamine, polyethyleneimineand a lipid.
 17. A method as in claim 1, wherein said composition is inthe form of a granule.
 18. A method as in claim 1, wherein said activeagent is a medicinal selected from the group consisting of antibiotics,antineoplastic agents, anesthetics, vaccines, hormones,anti-inflammatories, analgesics, tranquilizers, cytokines, colonystimulating factors, antidepressants, antiseptics, cardiovascular agentsanti-addictives, and antihypertensives.
 19. A method as in claim 18,wherein said medicinal is a salt.
 20. A method as in claim 18, whereinsaid medicinal is at least two medicinals of varying a polar character.21. A method as in claim 1, wherein said active agent is a drugprecursor.
 22. A method as in claim 1, wherein said active agent is aprotein medicinal.
 23. A method as in claim 22, wherein said proteinmedicinal is growth hormone.
 24. A method as in claim 1, wherein saidactive agent is imipenem.
 25. A method as in claim 1, wherein saidactive agent, is lidocaine.
 26. A method as in claim 1, wherein saidactive agent is selected from the group consisting of G-CSF, GM-CSF, andM-CSF; erythropoietin, IL-2, IL-4, IL-6; interferon, tumor necrosisfactor (TNF).
 27. A method as in claim 1, wherein said active agent isselected from the group consisting of epidermal-GF, nerve-GF, ACTH;angiotensin, atrial natriuretic peptide, bradykynin, dynorphin,endorphin, β-lipotropin fragment, enkephalin, gastrin, glucacon, growthhormone, growth hormone releasing factor, luteinizing hormone, releasinghormone, melanocyte stimulating hormone, neurotensin, opiode peptide,oxytocin, vasopressin, vasotocin, somatostatin, substance P, FactorVIII, TPA, streptokinase, glucocerebrosidase, hexoseaminidase A, tetanustoxoid and diptheria toxoid.
 28. A method as in claim 1, wherein saidactive agent is a nutrient.
 29. A method as in claim 1, wherein saidmatrix polymer is selected from the group consisting ofpolyethyleneglycol, polyvinylpyrrolidone, polyvinylalcohol, starch,xanthan, and cellulose.
 30. A method as in claim 28 or 29 furthercomprising amikacin.
 31. A method as in claim 28 or 29 furthercomprising silver sulfadiazine.
 32. A method as in claim 1 wherein saidsolid composition is porous.
 33. A method as in claim 1 comprising anactive agent, calcium sulfate and dextran sulfate.
 34. A method as inclaim 1 comprising an active agent, calcium sulfate andpolyethyleneglycol.
 35. A method as in claim 1, wherein saidadministration is by subcutaneous injection.
 36. A method of producing adelivery system comprising: (i) mixing (a) calcium sulfate hemihydrate,(b) an active agent and (c) a matrix biopolymer, (ii) forming themixture of step (i) into a bead, wafer, tablet, sphere, granule orcylinder.
 37. A method as in claim 36, wherein said inorganic compoundis calcium sulfate hemihydrate and said active agent are premixed andthen added to said matrix biopolymer.
 38. A method of producing a solidcomposition for the controlled release of an active agent comprising thesteps of: (a) forming a particulate mixture comprising (i) calciumsulfate hemihydrate, and (ii) a solid active agent; and thereafter (b)adding to the particulate mixture of step (a) an aqueous solution of amatrix polymer in an amount sufficient to hydrate the calcium sulfatehemihydrate to form a solid matrix containing the active agent, and toslow the release of said active agent therefrom, and (c) forming themixture of step (b) into a bead, wafer, tablet, sphere, granule orcylinder.
 39. A method of producing a solid composition for controlledrelease of an active agent comprising the steps of: (i) forming amixture of (a) calcium sulfate hemihydrate, (b) an active agent (c) amatrix polymer in an amount sufficient to slow the release of saidactive agent, and (d) water in an amount sufficient to form a solidmatrix due to the hydration of said calcium sulfate hemihydrate; and(ii) prior to formation of the mixture of step (i) into a solid matrix,shaping the mixture of step (i) into a bead, wafer, tablet, sphere,granule or cylinder.